Going Away? Make Sure Your Electric Car Stays Happy Without You

Electric cars, just like every other device or machine that relies on rechargeable batteries, slowly discharge over time. Leave them in low state of charge for too long, and their traction battery packs are destroyed.

Which is why automakers like Nissan and Chevrolet recommend owners follow specific instructions before leaving their Nissan Leaf and Chevy Volt cars for extended periods of time.

As we’ve proven, a 2011 Nissan Leaf will lose a few miles of charge if left unplugged in a semi-charged state for 8 days.

Leaving your car plugged into a suitable charging station while you’re away might seem like a sensible solution, especially if you time charging to finish just as you return.

There are two batteries

But as some Nissan Leaf owners over at MyNissanLeaf.com have discovered, leaving your Leaf plugged in while away could drain the car’s other battery — the one that runs its 12-volt accessory circuits.

Returning to their cars after a vacation or time away, these owners are reporting that their Leafs are unresponsive and often won’t unlock.

2011 Nissan Leaf SL
Just like almost every other car on sale in the U.S. today, cars like the 2012 Chevy Volt and 2012 Nissan Leaf have 12-volt accessory batteries that provide power to run onboard computers, entertainment systems, lights and wipers.

In a gasoline car, its 12-volt battery is kept charged by an alternator, powered by the car’s engine. In an electric car, a high-power dc-to-dc converter keeps the battery fully charged, fed by power from its traction battery pack.

It’s complicated…

In a car like the Nissan Leaf, its 12-volt battery will gradually discharge as it provides power to always-on systems like the alarm, locking system, radio and telematics computers.

When it gets too low and the car is unplugged, the Leaf’s 12-volt solar panel or dc-to-dc converter kicks in to charge it back up.

If the Leaf is plugged into a charging station and drawing power to charge its on-board traction battery pack, it should also charge up the 12-volt battery.

But when plugged into a charging station that is not actively charging the car, the Leaf enters into an operational mode that continuously looks to communicate with the charging station, drawing power as needed from its 12-volt accessory battery.

In this mode, the extra power drain can flatten the 12-volt battery — not the traction battery — in under a week.
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